Multiplex submarine cable



March 17. 1925.

W. H. MARTIN MULTIPLEX SUBMARINE CABLE IN V EN TOR. WZQ/Va/fm/ Filed Jan- 22. 1921 ATTORNEY Patented Mar. 17, 1925.

UNITED STATES WILLIAM E. MARTIN, or NEW YORK,

m TELEGRAPH COMPANY,

N. ASSIGNOB To a coarona'rron or new YORK.

TELEPHONE AJIERICAN MULTIPLEX SUBMARINE CABLE.

Application filed January 22, 1921. Serial No. 439,888.

T 0 all whom it may) concern:

Be it known that I, \Vnmuir II. MARTIN. residing at New York, in the county of Bronx and State of New York, have invented certain Improvements in Multiplex Submarine Cables, of which the following is a specification.

This invention relates to multiplex transmission systems. and more particularly to multiplex transmission systems for signaling over submarine cables.

In submarine cable systems it is customary to bring out the ocean cable proper at the shore into a small building known as a cable hut, and to connect the hut with a signaling station located at some more accessible or convenient part of the town or city by means of an extension of the cable or an inde endent conducting system, such, for examp e, as an underground cable. As is Well-known, a submarine cable may be a grounded circuit, and if the submarine cable is to be used for telephone transmission it'is undesirable that the cable system be continued as a grounded system from the cable but to the distant central ofiice, as a grounded conductor system in a city is impractical, because of interfering disturbances due to other signaling systems or power circuits or the like.

It is one of the purposes of this invention to overcome this diiliculty' in aisimple and yet eflicientmanner. Therefore, in accordance with the present invention the submarine cable is grounded at the but and a full metallic circuit is extended over an underground cable from the has to the distant central office, the full metallic circuit being associated with the cable circuit through a transformer which insulates the full metallic circuit from the grounded circuit. In order to obtain the fullest utility from the submarine cable circuit it is desirable that a plurality of signals be simultaneously superposed upon the circuit, or, in other words, that the cable be operated upon a multiplex basis, and the present invention therefore contemplates as one of its objects the multiplexing of a system of this character. Thefull metallic circuit extending through the underground cable may obviously serve asthe'co'mmon transmissionpath for a number of channels utilizing alternating currents as a transmitting medium; for example, it may serve to carry ordinary telencction. In accordance with the joined together phonic currents as well as one or more alternatin carrier frequencies for transmitring ad(itional signals. The full metallic cable circuit above referred to cannot be used, however, for transmitting direct current signals, because of the tranformer conpresent invention an'additional underground cable connection is therefore extended from the but to the distant central office, said cable connection being directly connected to the submarine cable and serving as a channel for the transmission of direct current signals. This additional underground cable connection is, of course, connected directly to the cable ground, but it is possible to o aerate this channel upon this basis, because t e disturbing electromotive forces encountered in the city do not so seriously affect the more powerful currents used in the transmission of direct current telegraph signals.

Other and further objects of the invention will be clear from the following detailed description when read in connection with the accompanying drawing, the figure of which is a schematic circuit arrangement of a multiplex signaling system embodying the invention.

Referring to the drawing, SC a grounded submarine cable terminating at the cable but A in the primary winding of a transformer T, the secondary of which is included in circuit with a full metallic cable circuit C extending from the but A to a distant central otfice B. At the central office B the metallic cable C is branched into a number of parallel transmitting paths, such as BL and BL, these paths being at their ends opposite the metallic cable C, and there associated with a designates balancing arrangement. The balancing ar-' rangement comprises a network N for simulating the metallic cable C, a transformer 'I" for simulating the transformer T, and an artificial line or network SN for simulating the submarine cable SC.

Transmitting and receiving channels may be associated with each of the branch paths; for example, a receiving tele hone channel L is shown associated with path BL through a balancing transformer arrangement 12, the corresponding transmitting channel TL bein connected to said path at the midpoints o the windings of the transformer 12, so that the channels the parallel i 'fiers may be of an vinterference with other si receiving amplifier and TL and RL are substantially conjugate. Each channel includes an ampllfier, the transmitting amplifier TA. being included in the transmitting channel TL,,' and the receiving amplifier RA; bein included 1n the receiving channel RL ese ampliwell-known construction, as, for examp e, vacuum tube amphfiers such as are used in ordinary telephone ractice. For the purpose of preventing naling channels a band filter TI is inclu ed in the transnitting channel TL. ,.and a band filter RF is included in'the receiving channel RL These filters are of the type-disclosed in the U. S. patents to George A. Campbell, Nos. 1227113 and 1227114, issued May 22nd, 1917, and are so designed as to transmit frequencies lying within the ordinary voice range; for example, from 275 cyclesvto 2300 cycles.

In a similar manner a carrier receiving channel RL may be associated with the parallel path BL through a balanced transformer 13, and the corresponding transmitting channel TL is associated with said parallel path by connecting it to the midpoints of the windings of the transformer 13. These channels may be used for the transmission and reception of telegraph signals by means of a suitable carrier frequency above the voice ran e. Consequently, a tuned circuit or other tering arran ement TF is included in the channel L and a band filter BI" of the Campbell type is included in the receiving channel RL These filtering arrangements are designed to prevent interference with other channels. .The transmitting channel TL also includes a transmitting oscillator and amplifier arrangement of a well-known construction. The transmitting oscillator may, for example, be a vacuum tube occillator whosecircuit is controlled by a sending relay SR to interrupt or modulate the carrier oscil' lations produced by the oscillator. The amplifier, which may in practice be included in the output circuit of the oscillator, may be any well-known type of amplifier, such as the vacuum tube amplifier. The receiving channel RL is also provided'with a detector RA,. The receiving amplifier may likewise be of the well-known vacuum tube construction, and the detector may be of any well-known character, such, for example, as the vacuum tube detector. In circuit with the detector is a receiving relay RR for transmitting the received detected signals to a receiving circuit.

In order to provide a channel for the transmission of direct current signals such as telegraph signals, an underground cable C extending from the but A to the central oflice- B is bridged across the submarine cable SC on the primary side of the transformer T. The cable G at the central oflice terminatesin a branch path BL,, similar to the branch paths BL and BL said branch path at its opposite end being connected'to a balancing arrangement comprising a network N, for simulating the cableC, and the artificial line or network SN, to which the ath BL, is connected in a manner similar to that by which the underground cable C,

is connected. with the submarine cable SC. In order to prevent shunting of the te'le-. phone and carrier currents through the capacity of the cable 0,, a retard coil 20 is inserted in the cable C, at the cable but and a similar coil 20' is included in the circuit BL for balancing urposes. A similar retard coil 21 shunte by a capacity 22 is inserted in the branch path BL, at one side of the midpoint thereof and a similar balancing combination 21'-22 is included in said path on the opposite side of the midpoint thereof. The retard coil 21 denser 22 coacts with the retard coil 20 and the capacity of the cable C to form a filtering arrangement which freely transmits the low frequency direct current sig nals but offers a very large impedance to the higher frequency telephone and carrier currents. The Morse signaling apparatus associated with the branch path BL, comprises a four-winding differential receiving relay RR, of well-known type, having its terminals bridged across the midpoint of the path BL, on one side and. connected on the other side to a balancing network TN,'. The transmitting channel TL is connected to midpoints of the windings of the difierential relay RR, and includes a. filtering arrangement comprising a retard coil 23 and condenser 24. A winding relay SR, is arranged to send positive or negative impulses over the channel TL, in a well-known manner. The receiving channel RL is-controlled by an auxiliary receiving relay RR,',

which in turn is controlled by the main receiving relay BB i The operation is as rents operate the sending relay SR, to transmit positive or negative impulses through the filter 23-2 1 to the midpoints of the windings of the receiving relay RR,. The energy If follows: Morse curdivides at this point, one ha being transmitted to the balancing network TN and the other half to the midpoints of the branch path BL,,'where the energy of the transmitted currents again divides, one half flowing through the balancing cable N to the network SN, the other half flowing over the cable C, to the submarine cable SC. Similar currents received from the cable SC pass over the underground cable G, into the, branch path BL, to operate the receiving relay RR,, which in turn. causes.the auxiliary relay RR, to transmit positive or 'alternatin imsubmarine ca 'le SO.

. lay

pulses through. the receiving channel R t the same time telephone currents may be transmitted through the transmitting amplifier TA over the channel TL, throng the filter TF to the midpoints of the windings of the transformer 12, where the energy divides, part flowing to the balancing i'rangement and art flowing over the cable C and throu h t e. transformer T'to the Received telephone currents incoming from the cable SC pass through the transformer T over theunderground cable C and through the transformer 12 to the receiving channel RL Where they ass through the filter RF to (1 by the amplifier HA The filter RF prevents currents lying without the Voice range-from entering the receiving channel. I 1 7 Similarly, Morse currents operating the sending relay SR cause Morse signals to be superposed on the carrier frequency generated by the transmitting oscillator and amplifier TA,, and the resulting currents are transmitted through the filter TF to the midpoints of the windings of the trans-.

former 13, where the energy divides, half flowing to the balancing arrangement, and the other half through the branchvcircuit BL, and over the u derground cable 0 to the cable SC. Similar carrier currents received from the cable SO pass through the transformer T .over the underground cable C and branch path BL, through the transformer 13 into the receiving channel RL where the are selected by the band filter RF amphfied by the amplifying portion of the arrangement RA and detached by the detector of the combination RA,. The detected currents o erate the receiving re- RR, to transmit Morse signals to the Morse line. The filters TF and RF prevent currents of frequencies other than the frequencies assigned to these channels from entering the channels TL and RL,. The parallel conductors connected to the channels TL and RL indicate the manner in which additional transmitting and receiving channels may be impressed upon the branch circuit BL through the common balancing transformer 13. It will be understood that each' of these transmitting and receiving channels will include filtering arrangements and translating devices similar to those included in the channels TL and R11 these filters and translating arrangements being designed with reference, however, to the transmission of other carrier frequencies than those employed by the channels TL and RL It will be obvious that the general principles herein disclosed may be embodied in many other organizations widely' difierent from those illustrated, Without departing I grounded conductor upon which metallic circuit at said distant from the spirit of the invention as defined in the following claims. What is claimed is 1. Ina multiplex transmission system, a

grounded transmission path upon which a plurality of si naling channels may be superposed, afu l metallic circuit associated with said grounded conductor, means forinsulating said full metallic circuit from said grounded conductor while permitting the transmission of alternating currents, means for superposing a plurality of two-way signalingchannels upon said full metallic circuit, connected to said grounded circuit, and means for transmitting direct current signals over said additional circuit. a

2. In a multiplex transmission system, a a plurality of'slgnaling channels may be superposed, a full metal ic circuit associated I grounded conductor and extending from the .terminal thereof to a distant point, means for insulating said full metallic circuit from said grounded conductor while permitting the transmission of alternating currents, a plurality of two-way signalin channels associated with said full metal ic circuit, an additional conducting system galvanically connected to said grounded conductor also extending to said distant point, and means at said distant point whereby direct current signals may be transmitted over said additional conductor and said grounded conductor. e

3. In a multiplex transmission system, a submarine cable terminating at the shore in a ground connection, a full metallic circuit associated with said cable and extending from the shore to a distant point, means for insulating said full metallic circuit from said grounded cablewhile permitting the transmission of alternating currents, means for superposing a pluralit of two-way signaling channels upon sai full metallic circuit, an additional conductor galvanically connected with said submarine cable and extending from the shore to said distant point, and means at said distant point whereby direct current signals may be transmitted over said additional conductor and said submarine cable.

4. In a multiplex signaling system, a submarine cable terminating at the shore in a ground connection, a full metallic circuit extendingfrom the hore to a distant point, means for insulating said full metallic circuit from said submarine cable while permitting the transmission of alternating currents, branch paths connected to said full point, said branch paths being joined at their opposite ends to balancing apparatus for balancing said submarine cable, full metallic circuit and associated apparatus, transmitting and an additional circuit galvanically with said receiving channels associated with each ductor being galvanically connected to said parallel path, an additional conductor exsubmarine cable and connected at said distendin from the shore to said distant point, tant point with said balancing apparatus, said a ditional conductor being galvamcally transmitting and receiving apparatus assoconnected to said submarine cable and being ciated Withxeach of said branch paths and similarly connected at said distant point said additional conductor at said distant to said balancing apparatus, and apparatus point, a retard coil included in said addiassociated. with said additional conductor tional conductor at a point near its junction wherebydirect currents may be transmitted with the submarine cable, filter apparatus to and received from said submarine cable. included in said additional conductor at said 5. In a multiplex transmission system, a distant point, said retard coil, together with submarine cable terminating at the shore in the capacity of said additional conductor, a ground connection, a full metallic circuit functioning with said filter apparatus to extending from the shore to a distant point, form a filter, ermitting the passage of curmeans for insulating said full metallic conrents of low reqnencyover said additional nection from the submarine cable While perconductor, but preventing the transmission mitting the transmission of alternating cnrof higher frequency currents from other rents, a plurality of branch paths leading channels. from said full metallic cirruit at the distant In testimony whereof, I have signed my station and connected together at their oppo name to this specification this 21st day of site ends with balancing apparatus, an addi- January 1921.

tional conductor extending from the shore to said distant point, said additional con- WILLIAM H. MARTIN. 

